Field of the Invention
Embodiments of the present invention relate generally to a multi charged particle beam apparatus, and a shape adjustment method of multi charged particle beam image, and more specifically, relate, for example, to a method for adjusting the shape of a multi-beam image in multi-beam writing using electron beams.
Description of Related Art
The lithography technique that advances miniaturization of semiconductor devices is extremely important as a unique process whereby patterns are formed in semiconductor manufacturing. In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits becomes progressively narrower year by year. The electron beam writing technique, which intrinsically has excellent resolution, is used for writing or “drawing” patterns on a wafer and the like with electron beams.
As a known example of employing the electron beam writing technique, there is a writing apparatus using multi-beams. Since it is possible for multi-beam writing to irradiate multiple beams at a time, the writing throughput can be greatly increased in comparison with single beam writing. A writing apparatus employing the multi-beam technique, for example, forms multi-beams by letting portions of an electron beam emitted from an electron gun pass through a corresponding hole of a plurality of holes in a mask, performs blanking control for each beam, reduces each unblocked beam by an optical system, and deflects it by a deflector so as to irradiate a desired position on a target object or “sample”.
In multi-beam writing, the shape of an aperture array, which forms multi-beams, directly affects the accuracy of connection of writing figures. Therefore, adjustment of magnification and/or rotation of a multi-beam image to be formed is very important. However, since the current density of each beam is around several A/cm2, it is difficult to accurately measure the position of each beam. Then, in order to obtain an S/N ratio, mark scanning operations of many times need to be performed using the same beam. Furthermore, since the size of the region of the aperture array is as large as several tens to several hundred μm, and therefore, the number of beams is large, it is difficult to accurately measure the shape of the image of the whole multi-beams. Accordingly, it becomes difficult to adjust the shape of a multi-beam image on the target object surface.
There is proposed a method for measuring a drift amount in a forming section of multi-beams by forming a plurality of measurement beams on the circumference of the multi-beams for writing, arranging detectors of the same number as the number of measurement beams near the height position of the crossover of the multi beams, and detecting positions of a plurality of measurement beams simultaneously (for example, refer to Japanese Patent Application Laid-open No. 2015-035489). However, it is difficult by this method to measure the shape of multi-beams on the surface of the target object.
The necessity of accurately measuring the shape of the image of the whole multi-beams is not limited to the case of the writing apparatus, and is important for general multi-beam apparatus using electron beams, etc. For example, it is also similarly important for an inspection apparatus, etc. which inspects patterns formed on the target object by multiple electron beams, etc.